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cowboy_social_google.erl
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cowboy_social_google.erl
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%%
%% @doc Handler for social login via OAuth2 providers.
%%
-module(cowboy_social_google).
-author('Vladimir Dronnikov <dronnikov@gmail.com>').
-behaviour(cowboy_http_handler).
-export([init/3, terminate/3, handle/2]).
%%
%%------------------------------------------------------------------------------
%% OAUTH2 Application flow
%%------------------------------------------------------------------------------
%%
init(_Transport, Req, Opts) ->
{ok, Req, Opts}.
terminate(_Reason, _Req, _State) ->
ok.
%%
%% {"/auth/google/:action", cowboy_social_google, [...]}.
%%
handle(Req, Opts) ->
% extract flow action name
{Action, Req2} = cowboy_req:binding(action, Req),
% perform flow action
{ok, Req3} = handle_request(Action, Req2, Opts),
{ok, Req3, undefined}.
%%
%% redirect to provider authorization page, expect it to redirect
%% to our next handler
%%
handle_request(<<"login">>, Req, Opts) ->
{SelfUri, Req2} = cowboy_req:host_url(Req),
CallbackUrl = << SelfUri/binary, (key(callback_uri, Opts))/binary >>,
AuthUrl = << (authorize_url())/binary, $?,
(cowboy_request:urlencode([
{<<"client_id">>, key(client_id, Opts)},
{<<"redirect_uri">>, CallbackUrl},
{<<"response_type">>, <<"code">>},
{<<"scope">>, key(scope, Opts)}
]))/binary >>,
cowboy_req:reply(303, [{<<"location">>, AuthUrl}], <<>>, Req2);
%%
%% provider redirected back to us with authorization code
%%
handle_request(<<"callback">>, Req, Opts) ->
case cowboy_req:qs_val(<<"code">>, Req) of
{undefined, Req2} ->
finish({error, nocode}, Req2, Opts);
{Code, Req2} ->
get_access_token(Code, Req2, Opts)
end;
%%
%% catchall
%%
handle_request(_, Req, _) ->
{ok, Req2} = cowboy_req:reply(404, [], <<>>, Req),
{ok, Req2, undefined}.
%%
%% exchange authorization code for auth token
%%
get_access_token(Code, Req, Opts) ->
{SelfUri, Req2} = cowboy_req:host_url(Req),
CallbackUrl = << SelfUri/binary, (key(callback_uri, Opts))/binary >>,
case cowboy_request:post_for_json(token_url(), [
{<<"code">>, Code},
{<<"client_id">>, key(client_id, Opts)},
{<<"client_secret">>, key(client_secret, Opts)},
{<<"redirect_uri">>, CallbackUrl},
{<<"grant_type">>, <<"authorization_code">>}
])
of
{ok, Auth} ->
get_user_profile(Auth, Req2, Opts);
_ ->
finish({error, notoken}, Req2, Opts)
end.
%%
%% use auth tocken to extract info from user profile
%%
get_user_profile(Auth, Req, Opts) ->
AccessToken = key(<<"access_token">>, Auth),
case cowboy_request:get_json(profile_url(), [
{<<"access_token">>, AccessToken}
])
of
{ok, Profile} ->
finish({ok, normalize_profile(Auth, Profile)}, Req, Opts);
_ ->
finish({error, noprofile}, Req, Opts)
end.
%%
%% finalize application flow by calling callback handler
%%
finish(Status, Req, Opts) ->
{M, F} = key(handler, Opts),
M:F(Status, Req).
%%
%%------------------------------------------------------------------------------
%% Helpers
%%------------------------------------------------------------------------------
%%
key(Key, List) ->
{_, Value} = lists:keyfind(Key, 1, List),
Value.
authorize_url() ->
<<"https://accounts.google.com/o/oauth2/auth">>.
token_url() ->
<<"https://accounts.google.com/o/oauth2/token">>.
profile_url() ->
<<"https://www.googleapis.com/oauth2/v1/userinfo">>.
normalize_profile(_Auth, Raw) ->
[
{id, << "google:", (key(<<"id">>, Raw))/binary >>},
{provider, <<"google">>},
{email, key(<<"email">>, Raw)},
{name, key(<<"name">>, Raw)},
{avatar, key(<<"picture">>, Raw)},
{gender, key(<<"gender">>, Raw)},
{locale, key(<<"locale">>, Raw)}
].